Is hand checking acceptable in streetball or is it fouling? For example when a player is driving to the hoop can you have the back of your hand on his waist while hes driving, not pushing him, just keeping it there to stay with him.

The way you described is perfectly fine. However, folks often have different definitions of hand checking. If a player is using a hand or forearm as a means to push me and displace me on a drive, I'll sometimes call a foul, but that's usually reserved for the most extreme situations.

Typically, I'll let most hand and arm contact slide. It's only when things go above and beyond, where a defender becomes singularly reliant upon the push or displacement in order to prevent me from getting to the rim or moving from point A to point B.